Category: Galling & Wear
Mechanical & Physical Properties
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Galling, sometimes known as cold welding, is a form of severe adhesive wear which can occur when two metals are in relative motion and under sufficient load to permit the transfer of material. Severe galling can result in seizure of metal components. The key factors affecting the tendency for galling are design tolerances and the surface finish, hardness and microstructure of the metals in contact.
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Coefficients of friction are more dependent on surface rather than material properties. Surface finish, cleanliness and lubrication of the mating surfaces largely determine the actual frictional resistance between mating surfaces. Surface finish, mating tolerances and lubrication play an important role in preventing galling and seizure.
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Galling, (cold welding), is a form of severe adhesive wear. The mechanism is briefly described. Soft very ductile austenitic stainless steel types tend to gall or seize where high stresses and poor lubrication are present. The factors affecting galling are covered, particularly design tolerances, surface finish, hardness and microstructure. Selection of grades to avoid galling covers Nitronic 32 and Nitronic 60 types. Fasteners to BS EN ISO 3506 with property classes 70 and 80 are also mentioned. The galling characteristics of duplex stainless steels is claimed by one US manufacturer to be similar to austenitic stainless steels. Methods for reducing galling tendency are discussed and include lubrication, nitriding and hard chromium plating.
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Galling, sometimes known as cold welding, is a form of severe adhesive wear which can occur when two metals are in relative motion and under sufficient load to permit the transfer of material. Austenitic and precipitation hardening stainless steels have poor resistance to galling. Hardenable martensitic stainless steels have better galling resistance. The galling characteristics of duplex stainless steels is thought to be similar to that of austenitic stainless steels.
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Galling, sometimes known as cold welding, is a form of severe adhesive wear which can occur when two metals are in relative motion and under sufficient load to permit the transfer of material. Lubrication in improves galling resistance. A solid lubrication system such as a PTFE coating gives better galling resistance than greases. Altering the surface characteristics by nitriding or chromium plating also improves wear and galling resistance.
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